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12 coins

  1. Dec 7, 2005 #1
    You have twelve coins, eleven identical and one different. You do not know whether the "odd" coin is lighter or heavier than the others. Someone gives you a balance and three chances to use it. The question is: How can you make just three weighings on the balance and find out not only which coin is the "odd" coin, but also whether it's heavier or lighter?
  2. jcsd
  3. Dec 10, 2005 #2


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    this has been posted here repeatedly. There's a variation to this coin problem that is much more complex, I saw it at "ibm ponder this" a couple of years ago....it makes this problem seem too easy. You can search there "ponder this" database if you want a real challenge.
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